Have a look at your contract and look if there is any mention of periods like christmas, half-term or easter as periods that you are required to work full time.

i know some jobs in retail include clauses that mention you are not allowed holidays during the few months running to christmas. Your contract may have a similar clause.

I have a link to the citizen's advice bureau. i will paste it down there.

http://www.adviceguide.org.uk/index/life/employment/young_people_and_employment.htm#hoursofworkandrestbreaks

Please read the section that concerns 'Hours of work & Rest breaks'.

It says you can only work

40 hours maximum in a week

8 hours maximum in a day (excluding breaks)

A MINIMUM OF TWO DAYS OFF IN THAT WEEK!

You are entitled time off work for studying or training. I suppose you should do such a thing as long as you provide reasonable notice, which in this case may be too late.

That is mentioned in the section 'Time off for studying or training'.

Stand up to them mate. Don't let your employers step over your toe! It's not about confrontation, but if you don't say anything, you and your fellow employees will keep being victims to such trade.

You're part-time they can make you work up to 24 hrs a week

full time is 38-40 hrs a week.

talk to the manager or the person who manages the schedule and ask them to book you less time.

You must mean McDonalds right? But as for an answer look up the local labor laws for minors in your state because since you are still in high school you should be able to work more than a certain amount of hours per day plus past a certain time at night on days preceding a school day. Express concern to your manager especially if it is in your job title that you only work 10 hours if your manager does nothing go to the general manager or there should be a employee number or Human resources number to call and tell them everything. They will definetely do something about it because if the labor dept. finds out they will fine the corporation.

There are loads of potential problems for teenagers in work, many of them legislative, parents need to be careful about that. There is loads of help from the resource in the box below on this issue, they also have help for all people who are searching for work, or who need to change careers.